1. Field of the Invention
The present invention relates to a vehicle lighting device employed in a rear combination lamp or a fog lamp, etc., including an automobile headlamp, and in particular, to a projector-type vehicle lighting device in which direct light from a light source and light reflected by a reflector are focused by means of a projecting lens, and are radiated to the forward direction of a vehicle.
2. Description of the Related Art
Conventionally, as disclosed in Japanese Laid-open Patent Application No. 2007-109613, a projector-type vehicle lighting device is known as the one that constitutes a light source unit by integrally molding a lens holder for holding and fixing a projecting lens and a reflector with an appropriate synthetic resin material and assembling them with a heat sink member in which a light source made of a semiconductor-type light emitting element such as an LED is arranged.
In the conventional vehicle lighting device, a light source is arranged in a heat sink member, thus improving a heat radiation effect at the periphery of the light source, whereas a lens holder is made up of a synthetic resin material provided separately, thus increasing a temperature at the periphery of a projecting lens. Due to this temperature difference, a lens holder portion may be slightly thermally deformed.
In addition, the semiconductor-type light emitting element has a small heat value in comparison with a halogen lamp or an HID lamp (High Intensity Discharge lamp). Therefore, in recent years, a synthetic resin-based lens which is lighter than a glass lens in weight has been used as a projecting lens more frequently. In a case where this synthetic resin lens is employed as a projecting lens, distortion may occur to the projecting lens due to the aforementioned thermal effect.
Thus, if the lens holder portion is slightly deformed due to the thermal effect at the periphery of the projecting lens, or alternatively, if slight distortion occurs to the projecting lens itself, slight aberration occurs to an optical design between the projecting lens and the light source and the reflector, adversely affecting light distribution performance.
Therefore, the present invention aims to provide a projector-type vehicle lighting device which is capable of improving an overall heat radiation effect of a light source unit and eliminating a temperature difference between the periphery of a light source and the periphery of a projecting lens.